The overall goal of this project is to develop a replacement for hormone delivery pumps with implantable capsules that rupture at predetermined times i.e., "pulse released". Feasibility will be demonstrated if, in Phase I, a polylactic/glycolic acid polymer formulation is prepared with mechanical properties favoring predictable burst, and a method for producing spheres of precise size and polymer coating thickness is demonstrated. Validation of implantable bursting capsules as a novel pulsatile hormone delivery system for research (and also clinical) applications, validity measured by both delivery and stress modulation.